provider/aws: Add support for ACM certificates to (#12592)
provider/aws: Add support for ACM certificates to (#12592)

api_gateway_domain_name

Fixes: #12566

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSAPIGatewayDomainName_'         ✹
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/03/10 19:32:31 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSAPIGatewayDomainName_ -timeout 120m
=== RUN   TestAccAWSAPIGatewayDomainName_basic
--- PASS: TestAccAWSAPIGatewayDomainName_basic (54.06s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/aws	54.091s
```
terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,terraform-providers/terraform-provider-aws,ashinohara/terraform-provider-aws,ClementCunin/terraform-provider-aws,ClementCunin/terraform-provider-aws,Ninir/terraform-provider-aws,nbaztec/terraform-provider-aws,kjmkznr/terraform-provider-aws,ashinohara/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,nbaztec/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,ClementCunin/terraform-provider-aws,ashinohara/terraform-provider-aws,nbaztec/terraform-provider-aws,Ninir/terraform-provider-aws,kjmkznr/terraform-provider-aws,charles-at-geospock/terraform-provider-aws